Due to increased environmental consciousness and political and economic concerns associated with the importation of foreign petroleum products, electric vehicles have been considered as alternatives to traditional internal combustion engine vehicles. However, significant transition from use of internal combustion engine vehicles to electric vehicles or hybrid electric/combustion engine vehicles has not been realized due to numerous challenges and disadvantages.
For example, an existing challenge is the relatively short range of electric vehicles utilizing batteries coupled with battery recharge times that may be significantly larger than the usage time of the battery. This shortcoming has been addressed by various approaches employing magnetic induction (also known as inductive coupling) to power vehicles and/or charge vehicle batteries.
To achieve inductive coupling of energy between physically separate elements, a primary coil may be electrically coupled to a current source such that the flow of current through the primary coil induces a magnetic field surrounding the primary coil. Current may be induced in a secondary coil when turns of the secondary coil cut through imaginary lines of flux of the magnetic field. The turns of the secondary coil may be caused to cut through magnetic lines of flux by producing relative motion between the primary and secondary coils and/or by causing the magnetic field to fluctuate using an alternating current source coupled to the primary coil.
In vehicles, magnetic induction powering has been proposed by providing a primary coil that is embedded in or near a roadway or path of vehicle travel and by affixing a secondary coil to the vehicle, such that the secondary coil moves with the vehicle, thereby producing relative motion between the primary and secondary coils. Presently, induction powering systems have been deployed only for charging stationary vehicles (e.g., in parking areas). However, such traditional approaches of applying magnetic induction powering are not without shortcomings.
As an example, one shortcoming is the distance between the primary coil and the secondary coil in traditional approaches. To provide clearance of the secondary coil from debris and other roadway hazards, traditional approaches provide an air gap between the roadway (having the primary coil) and a pick-up unit carrying the secondary coil. Such an air gap may reduce the effectiveness of magnetic induction, as inductive coupling between two coils decreases as the distance between the coils increases. A similar shortcoming is that traditional approaches do not ensure lateral alignment between the primary coil and the secondary coil. Due to such shortcoming, some vehicles, particularly those vehicles steered by a person, may stray from a centerline of a roadway, thereby reducing the inductive coupling between the primary and secondary coils. Additionally, another shortcoming of approaches pre-dating this disclosure is that the distance between the pavement and the secondary may continuously vary on a vehicle in motion due to horizontal motion of a vehicle in motion generated by the non-uniformity of pavement and the response of vehicle shock and struts.
As another example, the relative motion between a primary coil embedded in a roadway and a secondary coil mounted to a vehicle may not be sufficient to induce a sufficient amount of current in the secondary coil. While the current induced in the secondary coil may be increased by utilizing high-frequency alternating current in the primary coil, the resulting induced current may still remain insufficient to provide the necessary power or charging.
In addition, proposed methods to providing powering to a vehicle from a roadway may expose humans and other animals to high-frequency currents which may pose health and safety concerns.